My iphone5 purchased Jan 2013 at Walmart had always performed poorly when it came to registering network signals. But recently this winter, it has gotten to the point where it get's into a "Searching..." for network state that is very difficult to correct. I usually have to restart the phone or reset the network settings. And sometimes that doesn't even work.
I finally took the phone into the Apple store. The first solution was to provide me with a new SIM card. That seemed to have fixed the problem initially. But after 2 days, the problem came back. I went back to the Apple store a second time.
This time they took it into the back and after several minutes, came back and said that they opened it up and found that it was missing a component - the cowling over the video connector, camera connector, and proximity sensor. That cowling supposedly keeps all of the cables nicely fitted together. And without it, it's a possible reason why my phone continues to lose connectivity to the wireless network. He went on to say that it's possible that some one must have tampered with it before I got it from Walmart, and maybe taken the part to refurbish some other model. He said that it was evident that it was tampered with because there were fingerprints all inside. He proceeded to claim that this would have never passed QC at from the factory like that due to the measures they take - ensuring a uniform weight on every unit, down the the screw.
Of course that my phone was out of warranty and that it was already tampered with, they couldn't do anything for me. I was floored by just the mere notion of somehow this product making it out to market through a third party distibutor like Walmart. Afterall, when I purchased it, it was wrapped in cellophane, just like new.
Now after reading this post, I'm not sure if I'd blame 3rd parties like Walmart, or if Apple is actually covering up some serious QC issues.